In order to address the issue of increasing bandwidth requirements demanded for wireless communications systems, different schemes are being developed to allow multiple user terminals to communicate with a single access point by sharing the channel resources while achieving high data throughputs.
Certain wireless communications standards, such as the Institute of Electrical and Electronics Engineers (IEEE) 802.11 standard, denotes a set of Wireless Local Area Network (WLAN) air interface standards developed by the IEEE 802.11 committee for short-range communications (e.g., tens of meters to a few hundred meters).
Amendments 802.11ad, 802.11ay, and 802.11az to the WLAN standard define the MAC and PHY layers for very high throughput (VHT) in the 60 GHz range. Operations in the 60 GHz band allow the use of smaller antennas as compared to lower frequencies. However, as compared to operating in lower frequencies, radio waves around the 60 GHz band have high atmospheric attenuation and are subject to higher levels of absorption by atmospheric gases, rain, objects, and the like, resulting in higher free space loss. The higher free space loss can be compensated for by using many small antennas, for example arranged in a phased array.
Using a phased array, multiple antennas may be coordinated to form a coherent beam traveling in a desired direction (or beam), referred to as beamforming (BF). An electrical field may be rotated to change this direction. The resulting transmission is polarized based on the electrical field. A receiver may also include antennas which can adapt to match or adapt to changing transmission polarity.